Various radio access systems including mobile phones, wireless LANs, PHS and the like have spread and wireless MAN services such as WiMAX (Worldwide Interoperability for Microwave Access) (registered trademark) have started. In order to effectively utilize such access systems, research and development of a technology that hands over a different type of wireless network in a seamless manner has progressed (See Non Patent Documents 1 and 2).
Also, as disclosed in Non Patent Document 3, a software wireless technology capable of connection to a different wireless interface in order to switch to a different radio system has been studied.
Based on these technologies, limited radio resources (frequencies, wireless infrastructures) and network resources can be used more efficiently by switching to an optimal one in accordance with a state of the wireless network. Also, a throughput or capacity in total is improved by that and use efficiency of the frequency is improved.
For users, too, communication with optimal radio access is ensured all the time. For example, it is becoming possible to communicate with a mobile phone that supports high-speed movement during movement and to automatically switch to communication via a wireless LAN through an inexpensive internet line at home.
Non Patent Document 4 discloses Cognitive Wireless Cloud advocated by the applicant. The Cognitive Wireless Cloud is a cognitive wireless architecture in which a cognitive wireless terminal capable of connection to various types of networks through a plurality of radio access means autonomously collects information of a network available on the spot, obtains QoS information of each radio access or network on a real time basis, and optimizes capacity and an error rate of the entire network.
Supposing an environment in which a large number of radios are present, the total capacity is increased if a complex system as the entire network including the terminal is in an optimal state. As a result, a bit rate per frequency is improved, and the frequency use efficiency is improved.
The cognitive wireless network can be considered as a technology to form such optimal state while switching various types of radios.
In the past, when the measurement information of a radio system is to be collected or the setting is to be changed from a managing device, a function or information unique to the respective radio systems has been used. Therefore, in a device that integrates and manages radio access systems with different communication methods and management methods, devices developed for each radio system or network administrator are used.
Thus, functions in the device are different and interfaces between the devices cannot be made common. For this reason, it has been difficult to develop a general-purpose device that manages reconfiguration of various types of radio access devices.
As an example, IEEE 802.21 (See Non Patent Document 5) formulates specification to realize a handover, not relying on a type of radio, and has a function to control the handover by absorbing the type of radio. However, it relates to connection or disconnection of the wireless link and collection of wireless information and is not intended to optimize the radio access network.
Also, IEEE1900.4, which is a standard specification that defines a basic architecture and a function to optimally use radio resources by distributing decision making over the networks and terminals, was published on Feb. 27, 2009 (See Non Patent Document 6).
This specification will be described later, but in brief, in the previous proposals, the networks and the terminals are configured such that connecting methods can be reconfigured, respectively.
In connection with the present invention, the inventors have published many papers. For example, Non Patent Document 7 discloses a technology in which a terminal autonomously recognizes an available network, Non Patent Document 8 is a technology to obtain the respective network QoS information on a real time basis, and Non Patent Document 9 is a technology to make efficient radio resource reservations for a seamless handover that can support high-speed movement, respectively.
Also, related patent documents include Patent Document 1 that discloses a software wireless communicating device. This software wireless communicating device can support a plurality of frequencies and wireless methods by switching the software, since the received wave is analog-digital and converted by an AD converter once and a demodulation portion is handled by a digital signal processor or a microprocessor and the software.
The disclosed Patent Documents relating to the cognitive wireless system include Patent Document 2 that discloses a configuration to notify an empty wireless channel to a terminal device and particularly Patent Document 3 that proposes a method of determining presence of a radio wave.